Abstract： Objective To explore the pathogenic gene and mutation site of a patient with myxoid mitral valve disease and the family.Methods According to the results of whole exome sequencing in a patient with mitral regurgitation who had been admitted to the Valve Surgery Center,Beijing Anzhen Hospital,Capital Medical University due to myxoid mitral valve disease,blood samples were taken from the parents,brother and twin sister of the patient's family.Peripheral venous blood was collected to extract genomic DNA from the family members.Whole exome sequencing was performed on the proband's parents and siblings using a high-throughput sequencing platform.Suspected mutations were verified by Sanger sequencing in family members.Results Sequencing results showed that the proband and his sister had c.7819+1G＞A splice variant at the junction of exon 63 and intron 63 of the FBN1 gene.This mutation was a novel and pathogenic mutation.The myxoid mitral valve lesions in this family were syndromic.Conclusions FBN1 gene(NM000138.4)on chromosome 15 is the pathogenic gene.The c.7819+1 G＞A splice variant at the junction of exon 63 and intron 63 is reported for the first time in China and the third time in the world,which provides a basis for gene screening and treatment in the future.